The present invention relates to a mobile decorative nursery accessory and, more particularly, to a system for driving the mobile and a method of constructing the same.
Mobiles are well known for the amusement and entertainment of infants and young children. Typically, the mobile includes a number of objects, often brightly colored and of a shape such as would appeal to infants and children, suspended from one or more support arms. The mobile further includes an overhead support member, from which the support arms are hung such that the mobile is rotatable with respect to the overhead support member.
Normally, the rotation of the mobile is one of the features most entertaining to the infant or child. It is known, therefore, to provide a drive means for maintaining a constant rotation of the mobile. In U.S. Pat. No. 3,927,482, issued Dec. 23, 1975 to Marcus, for example, a mobile is disclosed wherein an electric motor powered by household current rotates the mobile.
In U.S. Pat. No. 4,207,696, issued June 17, 1980 to Hyman et al, a mobile is disclosed that is driven for rotation by a battery operated motor. In order to extend the useful life of the battery that powers the motor, an energy storage device is provided connecting the motor shaft with the mobile. The storage device is a cord, spring, wire or the like that is capable of being wound by the motor and subsequently unwinding itself. The motor is activated for only short periods of time so as to wind the storage device which then slowly unwinds so as to urge the mobile to rotate. The intermittent operation of the motor substantially conserves the useful life of the battery.
The preferred embodiment taught by the Hyman et al patent for the energy storage device utilizes a single cord of stranded hemp having a length of approximately four inches and a diameter of approximately 0.012 to 0.015 inches. As illustrated in the drawings of that patent, the cord is connected to the motor by tying the cord to a ring attached at the end of the motor drive shaft. Similarly, the cord is connected to the mobile by tying the cord to a ring formed at the end of a hook member connected in turn to the mobile support arms. Approximately three seconds of motor operation is sufficient to fully wind the cord, whereupon the mobile may be rotated for approximately 90 seconds before rewinding is necessary.
It can be readily seen, of course, that the greater the unwinding time provided by the energy storage device per unit time of motor energization, the greater will be the useful life extension of the battery. Moreover, a close examination of the particular hemp cord embodiment taught by the Hyman et al patent will reveal several disadvantages inherent in that particular energy storage device.
It has been found that the hemp cord has a relatively short useful life. The winding and unwinding of the cord tends to wear the fibers of the cord, resulting in its breakage, even after relatively little use. It can be seen, then, that replacement of the cord by the purchaser of the mobile will become necessary. Yet tying the cord at each end to connect it between the motor shaft and the mobile is, at best, a tedious operation.
These two disadvantages work together, resulting in great inconvenience to the purchaser.
It will also be readily apparent that the relative difficulty of attaching the cord by tying it to rings poses difficulties in the manufacture of the mobile.
What is needed, therefore, is an energy storage device for use with a motor driven mobile that will have a long useful life without rapid wear and subsequent breakage. Such a storage device should be relatively simple in its insertion into the mobile, both during initial manufacture of the toy and in the event subsequent replacement should become necessary. It should give a long unwinding period for rotating the mobile with only a very short energization period for the motor. Additionally, the energy storage device itself should be simple and inexpensive to manufacture.